Threaded container closure

ABSTRACT

The present invention is directed to a closure having a top wall which has a base cross-sectional thickness, a threaded portion and an annular skirt depending therefrom which includes tamper-evident means frangibly connected thereto. The top wall further comprises a stiffening block from which an inner annular seal and an outer annular seal depend. The inner annular seal is characterized by depending from a point of the stiffening block which is midway between the inner and outer periphery of the stiffening block and which is positioned to sealingly engage the inner wall of the opening of a container to which the closure is applied. The outer annular seal depends from the stiffening block in a manner such that the outer wall of the seal defines the outer periphery of the stiffening block. The stiffening block contains also a groove which defines the point of attachment of the inner wall of the outer seal and the sealing block and a step between the inner and outer seal which impinges the opening of a container to which the closure is affixed. This arrangement provides improved sealing and decoupling of stresses placed on the closure top wall from the sealing means.

FIELD OF THE INVENTION

The invention pertains to a closure for sealing the opening of acontainer and a package comprising the closure assembled onto acontainer.

BACKGROUND OF THE INVENTION

Closures for sealing a container comprising a top wall, dependingtherefrom a skirt having a threaded portion and attached thereto atamper-evident device are well known in the art. In particular, closureshaving a sealing means comprising an annular sealing member dependingfrom the top wall of the closure which is coaxial with the closure skirtare known also. An example of one such closure is described in U.S. Pat.No. 6,235,226 to Krautkramer, which employs an annular member defining asealing “olive” which enters the neck of a container onto which it isapplied and has a portion that seals with the internal surface of thecontainer neck. In addition to the sealing olive, the Krautkramerclosure has a second sealing member in the form of a ring which dependsfrom the top wall of the closure, coaxial with the closure skirt andlocated between the closure skirt and sealing olive. This second sealingmember impinges the opening of the container, making contact with theouter lip portion of the container opening, forming a second seal as theclosure is screwed onto the container. This arrangement produces twoseals on the container, an inner seal in which the inner wall of thecontainer opening places the sealing olive in compression, and an outerseal in which the sealing flap is placed in tension by the outer lip ofthe container opening.

As is known in the art, such closures are subject to over-torquing onapplication, making it difficult to remove the closure. In addition,such closures are subjected to loss of seal between the closure and thecontainer when a package comprising the closure assembled to a containeris subjected to shock, for example, dropping, or sudden changes inpressure which result in “bulging” of the closure (increases inpressure), or drawing the closure into the container (decrease inpressure). These events, termed herein for convenience as “doming”effect the manner in which both the inner and outer seals impinge thecontainer and can cause the seal to break and the container to leak. Inaddition, with these prior art closures, forces applied to the center ofthe closure during storage and handling after filling, for example,stacking of cases of bottles, are translated to the sealing means of theclosure with similar breaking of the seal and loss of sealing.

SUMMARY OF THE INVENTION

These and other deficiencies are met by the present invention. Thepresent invention provides a container closure having a top wall whichhas a base cross-sectional thickness and depending from the peripherythereof, an annular skirt having an internally threaded portion andfrangibly attached to the free edge of said annular skirt, atamper-evident means which includes means for engaging a feature on acontainer to which the closure is applied to facilitate separating saidtamper-evident means from said annular skirt at said frangibleconnection, and wherein the closure is further characterized by:

-   -   (a) a filled shoulder region between the top wall and said        annular skirt forming a substantially conical profile having a        face oriented toward the radial axis of the closure;    -   (b) an annular sealing means depending from said top wall and        centered on the radial axis of the closure, comprising:        -   (i) a stiffening block in the form of a ring of material            depending from said top wall coaxially with said annular            skirt, having an inner and outer periphery, the stiffening            block being characterized in having a cross-section thicker            than said top wall base thickness;        -   (ii) an annular outer seal depending from the stiffening            block proximal to said closure shoulder, having an outer            wall defining the outer periphery of said stiffening block            and an inner wall facing the radial axis of the closure, and            which is further characterized in having at least a portion            of the free end thereof which projects toward said annular            skirt;        -   (iii) an annular inner seal having an inner and an outer            wall depending from said stiffening block, said inner wall            defining a point of attachment to the stiffening block at a            point outboard of the edge of the inner periphery of said            stiffening block, said outer wall defining a point of            attachment to the stiffening block inboard of said inner            wall of the annular outer seal, the inner seal being further            characterized in projecting toward said annular skirt,            wherein said annular inner seal has a face directed toward            the radial axis of the closure which is substantially            conical and is further characterized by the outer wall            defining a surface having an outermost diameter greater than            the opening of a container to which the closure is applied            which enters into sealing engagement with the opening of            said container; and        -   (iv) an annular groove in said stiffening block which            defines the point of attachment of the inner wall of the            outer seal with the stiffening block and which is further            characterized by having a depth yielding a cross-sectional            thickness to the stiffening block which is at least as great            as the base thickness of the closure top wall and which is            disposed in the stiffening block to provide a step between            the point at which the outer wall of the inner annular seal            is attached to the stiffening block and the groove, the step            being positioned to impinge a portion of the inner edge of            the opening of a container to which the closure is attached,            wherein the diameter and length of said inner and outer seal            and the spacing between them are selected to accommodate a            container opening and place said outer seal in a biaxial            stretching condition against the lip of the container            opening.

In one embodiment of the present invention closure, the base thicknessof the top wall, and the cross-sectional thickness of the stiffeningblock and annular groove are selected such that doming of the cap due tostress is confined to the central region of the cap within the innerperiphery of said stiffening block.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional representation of a bisected portion of oneembodiment of a closure of the invention.

FIG. 2 details various cross-sectional features of the top wall andsealing means of one embodiment of a closure of the invention.

FIG. 3 further details various cross-sectional features of thestiffening block and inner and outer seals of one embodiment of aclosure of the invention.

The figures utilize numbers pointing out various features of theinventive closures wherein like numbers in different figures representlike features in the closure.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

European patent no. 0810951 to Thompson, and published InternationalApplication no. WO 03/074380 and the priority documents claimed thereindescribe several molded plastic closures, the details of which areincorporated in their entirety herein by reference. As illustrated inFIG. 1, the present invention improves on these molded plastic closuresby providing a closure which contains both a plug seal and an externalseal along with a closure top wall profile which decouples flexing inthe cap due to stacking or internal pressure changes in the container towhich the closure is applied from the sealing region of the cap.

The following description employs terms utilizing structuraldescription, for example, “point of attachment”. It is to be understoodthat no limitation regarding methods of forming the subject closures areinherent therein. Accordingly, it is contemplated that the closures ofthe invention will be prepared by any known means, including injectionmolding of plastics forming the closure as a single, monolithicstructure. It is to be understood that the term “closure” refers tomolded plastic closures as that term is understood by those of ordinaryskill in the art.

With reference to FIG. 1, one embodiment of the closure of the inventionprovides a closure having a top wall (1) from which an annular skirt (2)depends. Annular skirt (2) has an internally threaded portion (3) andfrangibly attached to the free edge of said annular skirt, atamper-evident means (4) which includes means (5) for engaging a featureon a container to which the closure is applied, thereby separating saidtamper-evident means from said annular skirt at said frangibleconnection (6) when the closure is removed from the container.

With reference to FIG. 2, the top wall of the closure (2) has a basecross-sectional thickness 21, and is further characterized by a filledshoulder region between said top wall and said annular skirt (22)forming a substantially conical profile having a face (23) orientedtoward the radial axis of the closure (24). With further reference toFIG. 1, depending from the top wall and centered on the radial axis ofthe closure is a stiffening block, a portion of the cross-section isdesignated as region (11) in the Figure. The stiffening block has theform of a ring of material having an inner (12) and outer periphery (13)depending from said top wall coaxially with said annular skirt. Incross-section (25), the stiffening block is thicker than said top wallbase thickness

With further reference to FIG. 2, integrally formed with and dependingfrom the stiffening block are an annular outer seal (26) and annularinner seal 27. Annular outer seal (26) has an outer wall (28), an innerwall (29) and a bulbous free end (30). The outer wall (28) of outer seal(26) defines the outer periphery of stiffening block (11) and isproximal to conical face 23 of the closure shoulder. Outer seal (26) isalso characterized by having a portion of the free end of the seal (200)projecting toward the annular skirt of the closure. Preferably, theprojection has the form of a bulbous section or bead appended to theedge of the outer wall of the seal. In use, when the closure is appliedto a container, a portion of the outer wall of the opening of thecontainer impinges the annular inner wall of the outer seal, forcingprojection (200) to contact face (23) of the closure shoulder. Uponcontact, and with continued tightening of the closure, the seal isexpanded axially by the impinging container opening and is stretchedradially by the bulbous feature rolling in contact with face (26) of theclosure shoulder region. Accordingly, the outer seal is placed intension in two directions, and thus is biaxially stressed in sealing thecontainer. This imparts improved resistance to breach the seal due todimensional changes in the container during storage or to shock andsudden pressure changes in handling and storage of the filled container.

With reference to FIG. 3, annular inner seal (27) has an inner (30) andan outer (31) wall depending from said stiffening block and projects inthe direction of the annular skirt. The point at which the inner wallattaches to the stiffening block (32) is outboard (radially) from theedge (33) of the inner periphery of said stiffening block. As mentionedabove, the inner seal is further characterized in projecting toward theannular skirt. This is shown in FIG. 3 as a line bisecting thecross-section of said inner seal (34) forms an obtuse angle (a) with aline (35) bisecting the cross-section of said top wall and passingthrough the radial axis (24) of the closure. In this manner, face 30,which is directed toward the radial axis of the closure, issubstantially conical. The cross-section of the free end of the innerseal may be reverse tapered or rounded such that upon initial contactwith a container opening, the inner seal presents a cross-sectionaldiameter which is smaller than the container opening, and thus presentslittle resistance to passing into the container opening. With referenceto FIG. 2, the maximum cross-sectional diameter presented to thecontainer opening (201) is selected to exceed the container opening,thus axially compressing the outer wall (31) of the inner seal andsealing it to the inner wall of a container opening to which the closureis applied.

With further reference to FIG. 3, the stiffening block contains also anannular groove (36) which is placed in the stiffening block in alocation defining the point at which the inner wall (29) of the outerseal joins the sealing block. The groove also defines a step (37) in thestiffening block between the inner edge of the groove and the point (38)at which the outer wall (31) of the inner seal joins the sealing block.The depth of groove 36 is selected to provide a minimum thickness in thegroove region which is at least as thick as the base thickness of theclosure top wall. The thickness of step (37) is selected to impinge theinner portion of the edge of the opening of a container to which theclosure is applied, acting as a stop which insures a satisfactory sealbetween the outer annular seal and the container without over tighteningthe closure. Accordingly, the diameter and length of said inner andouter seal and the spacing between them are selected to accommodate acontainer opening. The shape and length of the outer seal is selected toinsure that when the closure is applied to a container, the containeropening forces the bulbous projection of the outer seal to contact theconical face of the should region of the closure, placing the outer sealin a biaxial stretching condition against the lip of the containeropening. It is preferred if the length of the seals and the spacingbetween the seal and the threaded portion of the closure are selectedsuch that the seals are broken from engagement with a container to whichthe closure is applied before the threaded portions of the container andclosure disengage.

The cross-section thickness of the stiffening block in the variousregions described above relative to the base thickness of the capitself, permits the central portion of the cap to be relatively thin,permitting overall weight and materials savings, and allows the sealingregion to remain relatively free of the stresses effecting sealingduring handling and storage of a filled container. Accordingly, the basethickness of the closures top wall, and the cross-sectional thickness ofthe stiffening block and its attendant integral stop block and annulargroove are selected such that the comparatively thinner central top wallportion of the closure can be subjected to doming forces due to productstacking and pressure changes internally in the filled container, whichare decoupled from the periphery of the closure, and thus from strainingor impinging on the sealing features of the closure. Thus, permittinglonger storage and handling life to packages sealed with the closure.

Numerous tamper-evident means are known in the industry and cited in thepublications incorporated herein by reference. These publications areincorporated herein for illustration of tamper-evident means as well. Itis preferred if tamper-evident means include a ribbed frangible regionand include also a “winged” or “claw-like” radially projecting array offeatures directed to the radial axis of the closure. The dimensions andconfiguration of these projections will be selected for engagement witha feature on the finish of a container to which the closure is applied.As is known, such engagement promotes immobilization of thetamper-evident band when the closure is removed from the container,assisting in rupture of the frangible connection between the closure andthe tamper-evident band and retention of the band (as an indication ofcontainer breach) on the container.

Having described the presently preferred embodiments, it is to beunderstood that the invention may be otherwise embodied within the scopeof the appended claims.

1. A closure having a cross-section of the closure in FIG. 1 containinga plug sealing arrangement which engages the internal wall of acontainer opening upon application of the closure to the container, andwhich has a outer-lip sealing means that engages the outer-lip of thecontainer opening upon application of the closure to the container. 2.The closure of claim 1 wherein said inner and outer sealing meansdisengage from the container prior to said threaded portion disengagingfrom the container.
 3. A container closure having a top wall which has abase cross-sectional thickness and depending from the periphery thereof,an annular skirt having an internally threaded portion and frangiblyattached to the free edge of said annular skirt, a tamper-evident meanswhich includes means for engaging a feature on a container to which theclosure is applied to facilitate separating said tamper-evident meansfrom said annular skirt at said frangible connection, and wherein theclosure is further characterized by: a. a filled shoulder region betweensaid top wall and said annular skirt forming a substantially conicalprofile having a face oriented toward the radial axis of the closure; b.depending from said top wall and centered on the radial axis of theclosure, an annular sealing means comprising: (i) a stiffening blockdepending from said top wall coaxially with said annular skirt in theform of a ring of material having an inner and outer periphery which ischaracterized in having a cross-section thicker than said top wall basethickness; (ii) an annular outer seal depending from the stiffeningblock proximal to said closure shoulder, having an outer wall definingthe outer periphery of said stiffening block and an inner wall facingthe radial axis of the closure, and which is further characterized inhaving at least a portion of the free end thereof which projects towardsaid annular skirt; (iii) an annular inner seal having an inner and anouter wall depending from said stiffening block, said inner walldefining a point of attachment to the stiffening block at a pointoutboard of the edge of the inner periphery of said stiffening block,said outer wall defining a point of attachment to the stiffening blockinboard of said inner wall of the annular outer seal, the inner sealbeing further characterized in projecting toward said annular skirt, andwherein said annular inner seal has a face directed toward the radialaxis of the closure which is substantially conical and is furthercharacterized by the outer wall defining a surface having an outermostdiameter greater than the opening of a container to which the closure isapplied which enters into sealing engagement with the opening of saidcontainer; and (iv) an annular groove in said stiffening block whichdefines the point of attachment of the inner wall of said outer sealwith said stiffening block and which is further characterized by havinga depth yielding a cross-sectional thickness to the stiffening blockwhich is at least as great as the base thickness of the closure top walland which is disposed in the stiffening block to provide a step betweenthe point of attachment of the outer wall of said inner annular seal tosaid stiffening block and said groove, said step being positioned toimpinge a portion of the inner edge of the opening of a container towhich the closure is attached, wherein the diameter and length of saidinner and outer seal and the spacing between them are selected toaccommodate a container opening and place said outer seal in a biaxialstretching condition against the lip of the container opening.
 4. Theclosure of claim 3 wherein the base thickness of the top wall, and thecross-sectional thickness of the stiffening block and annular groove areselected such that doming of the cap due to stress is confined to thecentral region of the cap within the inner periphery of said stiffeningblock.
 5. A package comprising a container assembled with a closure ofclaims 1 to 4.